Andrews, P.W.S., author
Macmillan, 1949
Buku Teks
Griffin, Ricky W., author
Prentice-Hall, 2002
Buku Teks
Straub, Joseph T., author
Kent, 1985
Buku Teks
Madura, Jeff, author
South-Western College, 2001
Buku Teks
Ebert, Ronald J., author
Prentice-Hall, 1998
Buku Teks